The 3 differences between shared environment and non-shared environment

A summary of the differences between these concepts so often used in Psychology and Biology.

Since its foundation, Psychology has been a science that has tried to explain human behavior.

Since its foundation, Psychology has been the science that has tried to find explanations for why people behave in such different ways.

After decades of research and heated discussions about whether genetics or the environment is more influential in shaping a person's personality and behavior, the now more than famous debate on thethe now more than famous 'nature vs. nurture' debate has been overcome, giving both factors more or less equal prominence.

Our genes contain some of the causes that make us more similar to our parents than our neighbors, but the neighborhood we live in or the region we live in also influence our behavior.

Once the debate was over, we tried to understand something that happens in all families. Although siblings are very similar, there is always something that differentiates them. Their genotype, even if it is not exactly the same, cannot be. Neither should be the environment, because all family members receive the same influences from it, shouldn't they?

In this article we are going to address an aspect that has often been overlooked when it comes to understanding how the environment influences each of us with respect to our family members. Let's see how the shared environment differs from the non-shared one..

Differences between shared and unshared environment: an overview

Although tragic, the study of behavior, intelligence and personality in identical twins separated shortly after birth has been one of the most beneficial in understanding the extent to which certain phenotypic traits are heritable and which depend on the environment in which one is raised. The premise is that if two monozygotic twins, i.e., two clones genetically speaking, live in different homes, those aspects they share will be due to their genetics, while those that differ will be due to the environment and/or their interaction with the genotype of these individuals.

Thomas Bouchard is an American psychologist and geneticist who has studied pairs of twins separated at birth.. In his project, the Minnesota Study of Twins Reared Apart, he investigated how genetics and environment influence the personality of twins reared apart. In this type of study, genetics is given a great deal of importance, but it can be observed that the environment influences how people behave.

The environment is understood as the set of aspects external to the person that may or may not exert some kind of influence on the personality, cognitive capacity and behavior of the individual. and behavior of the individual. Studies of Bouchard's style take for granted that growing up in different homes implies different environments, while growing up in the same home tends to mean growing up in the same environment.

However, for some time now, and even raised in Bouchard's own study, the possibility has been raised that living in the same household, and thus being raised with other Biological siblings, need not mean receiving the same environmental influences. The reason for this is the obvious fact that siblings are not equal in behavior or abilities.

It is true that the siblings of the same family have not inherited the same genes each and every one of them, otherwise we would not speak of siblings as such, but of identical twins. However, the genetic basis is there, and that should imply that there are very few differences between siblings, which is rarely the case.

Even between monozygotic twins raised in the same household there are differences.. The differences must necessarily be explained by the environment, but, having been raised in the same home, how is it possible that there are behavioral differences as well?

This is when we talk about the shared environment and the non-shared environment, two factors within the concept of environment or environmental influences that allow us to understand the differences and similarities of the members of the same family. Let's go deeper into what these two concepts mean.

Shared environment

On many occasions, it has been assumed that living in the same family, home or neighborhood implies receiving the same environmental influences.

Actually, this definition corresponds to what is understood as shared environment, also called family environment, that is, those aspects coming from the environment that are shown in the same way to all the members of the same family and that, therefore, make them more similar to each other.

To understand it in a clearer way, an example of a shared environment would be the home in which the siblings live.. By living in the same house they all receive the same influence from it.

Another aspect that is considered a shared environment would be living in a bilingual region and therefore the siblings would be equally fluent in two languages because the environment demands it. By mastering two languages they would all have the same type of cognitive stimulation from the environment in which they were raised.

As a third example, there would be the socioeconomic level of the family. If it is the case of living in a wealthy family, none of the family members will suffer any kind of situation where there is any kind of nutritional deprivation due to not being able to buy food.

Since all the members of the family remain in the same environment, so it is shared, it is not possible to explain with this type of environment why there are differences between siblings.

Non-shared environment

The non-shared environment, also called individual environment, is understood in terms of influences rather than environment per se. This would be the set of factors external to the person that are interpreted in a different way depending on each member of the same family.

Returning to the case of monozygotic twins and, therefore, genetically identical, the non-shared environment would be the one that would explain why two twins with these characteristics, raised in the same family, would be different, the non-shared environment would explain why two twins with these characteristics, raised in the same place, may behave differently..

There are several environmental aspects that can influence siblings differently. For example, a twin sibling may have suffered more colds during his or her life, or may have been involved in a car accident.

Also, as a non-shared environmental factor the different treatment by parents that can occur in a child's life.. It is not uncommon to find pairs of twins in which one of the two calls himself the older of the two and, due to this small detail, behaves in a more mature way or believes that he should have more rights over the other, and the family environment promotes this.

Another very important aspect, always taking as an example the case of monozygotic twins, is education. Although at home they receive the same discipline, at school it is common that they do not attend the same class and, therefore, have different classmates and teachers.

Family events may be experienced differently between siblings.. For example, the death of a family member, something that is sad in itself, may be experienced in a much more sorrowful way by one of the siblings compared to the rest and affect them more deeply.

Beyond biology and genes

Both shared and unshared environments, in addition to genetics, are behind the way people are. However, it is worth noting that research indicates that the influence of the two types of environment is different depending on the evolutionary stage.. During childhood, the shared or family environment plays a fundamental role, being something that strongly shapes the person. With the passage of time, the influence of the family environment diminishes, and the non-shared or individual environment acquires greater importance.

In fact, as an example of this, a very generalized view among adults when asked about what they believe most influences the way a person is, is that genetic inheritance, together with one's own experiences (often leaving aside how one was raised) are factors to be taken into account that explain one's behavior. that explain one's behavior.

Obviously, this does not mean that extremely harmful childhood situations, such as situations of neglect and abuse, do not influence how a person may end up as an adult. However, leaving aside the extreme cases, more importance is usually given to heredity together with the individual stimuli that have been received throughout life.

Bibliographical references:

• Bouchard, T. J., Jr. et al. (1990), "Sources of human psychological differences: the Minnesota Study of Twins Reared Apart." Science, vol. 250, no. 4978, p. 223-228.
• Plomin, R. and Daniels, D. (2011), "Why are children in the same family so different from one another?". International Journal of Epidemiology, vol. 40, no. 3, p. 563-582.
• Plomin, R., et al. (2001), "Why are children in the same family so different? Nonshared environment a decade later". Canadian Journal of Psychiatry. Revue Canadienne de Psychiatrie, vol. 46, núm. 3, p. 225-233.
• Plomin, R. (2011), “Commentary: Why are children in the same family so different? Non-shared environment three decades later”. International Journal of Epidemiology, vol. 40, núm. 3, p. 582-592.